Over the last 3 years our laboratory, in collaboration with that of James Rothman, has found strong evidence that coated vesicles mediate the transport of a virus membrane glycoprotein, G protein, from its site of synthesis, the rough endoplasmic reticulum, to the plasma membrane. We are presently applying techniques developed in this study to the role of coated vesicles in the transport of newly synthesized procollagen and acetyl choline receptors in chick fibroblasts and myotubes, respectively.